The present invention relates to an electrode for use in iontophoresis therapy. In particular, the present invention relates to an iontophoresis electrode having a drug solution injection site and a reservoir for holding the solution during a treatment.
There is an ongoing search for methods of medical treatment which are non-invasive and painless. An effective treatment is useless if the patient refuses it due to the pain it can cause. Iontophoresis medication delivery systems are safe, effective, non-invasive, and relatively painless.
Iontophoresis involves the interaction between ionized molecules of a drug and an external electric field, resulting in the migration of charged molecules. The migration is achieved by placing two electrodes on the patient's skin which are connected to an electric DC power supply. One of the electrodes is an "active" electrode filled with a drug solution. The other electrode is an "inactive" or "indifferent" electrode filled with an electrolyte solution. The electric field generated between the two electrodes causes the charged drug molecules to migrate from the active electrode into the tissues and blood stream of the patient without the necessity of hypodermic injection and its adverse effects, such as pain and risk of infection.
Delivery of drugs via iontophoresis also presents the advantage of avoiding first-pass metabolism of the drug. When a drug is taken orally and absorbed from the digestive tract into the blood stream, the blood containing the drug first percolates through the liver, a metabolically active organ, before entering the general circulation for delivery to the target tissue. Thus, much of the orally ingested drug may be metabolically inactivated before it has a chance to exert its pharmacologic effect. Local delivery of drugs, therefore, presents advantages over oral administration, an application characterized by inefficiency and unpredictability, and over hypodermic injection, an invasive, inconvenient, and sometimes risky technique.
One factor that controls the effectiveness of iontophoresis is the design of the active, or drug delivery, electrode. Preferably, the drug delivery electrode includes an injection site that allows insertion of the drug solution before or during a treatment session. In this manner, the electrode may be stored, prior to treatment, in a "dry" state for an extended period of time without the risk of evaporation or leakage. The electrode should readily adhere to the patient's skin during treatment and should be flexible to facilitate a variety of electrode placements. The electrode should hold a volume of solution sufficient for the individual treatment session and should hold the solution for the allotted treatment time. Finally, the electrode should provide an adequate conductive surface area to prevent burning of the patient's skin.
Because the drug delivery electrodes are typically discarded after a single treatment session, these electrodes should therefore be of very low cost. However, drug delivery electrodes of the prior art typically include a plastic or rubber housing that forms a reservoir to hold the drug solution. Unfortunately, these housings are relatively expensive to manufacture. Thus, disposing each electrode after a single use becomes expensive. Even further, these housings are relatively stiff and do not adequately conform to the surface of the patient's skin during treatment. As a result, an inexpensive, flexible electrode having a low-profile is desired.